Combining the electrospinning process with UV photopolymerization allowed for the fabrication

Abstract

In this work, new drug delivery systems based on polymeric composite nanofibers as well as mesoporous nanoparticles were synthesized and evaluated with respect to their drug-loading capacity and release as well as antimicrobial properties. Through careful control of manufacturing protocols, electrospun biodegradable fiber mats and mesoporous silica nanoparticles (MSNs) with defined morphology and scalable diameter could be obtained.

Combining the electrospinning process with UV photopolymerization allowed for the fabrication

of thermosensitive core-shell polycaprolactone-poly(N-isopropylacrylamide) nanofibers which,

depending on the temperature of the milieu, provided different release kinetics of the loaded

antibiotic doxycycline hyclate (Doxy). The biocompatibility of those fiber mats was

demonstrated using in-vitro MTT assays, while the antimicrobial activity was proven via Kirby

Bauer diffusion assays. A dual drug release of rhodamine B and sparfloxacin was

demonstrated by incorporating drug-loaded MSNs into the electrospun mats. Synthesis of

MSNs with controlled size and homogenous porosity was achieved by combining the well-

known sol-gel process with an endo-template method. Moreover, the influence of surface

modification on release of Doxy was demonstrated by functionalizing MSNs before and after

drug loading with APTMS (3-Aminopropyltrimethoxysilane). The results demonstrated the

importance of performed modification steps that was crucial for the observed drug release, as

APTMS functionalization after drug loading resulted in lower and slower release of Doxy. To

determine the minimal inhibition concentration (MIC) of the antimicrobial molecule Doxy,

concentration-dependent studies on two different bacteria types, namely Escherichia coli and

Staphylococcus aureus were performed. Additionally, ellipsoid-shaped hollow mesoporous

silica capsules (HMSNs) were prepared based on etching of elongated core-shell hematite-

silica (SiO

@Fe

O

) particles and loaded with Doxy. Drug release kinetics of HMSNs and

MSNs revealed that the inner cavity of HMSNs provided not only higher loading capacities but

also high release rates of the encapsulated drug. In summary, results obtained in this work

demonstrate the promising potential and high biocompatibility of evaluated drug delivery

systems (nanofibers and MSNs and composite structures of both materials) and supports their

employment for drug release in biomedical applications.